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(No Model.)

G. T. WOODS.

TELEPHONE SYSTEM AND APPARATUS.

No. 371,241. Patented Oct. 1111887.

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i current of far greater inducing strength in the' UNITED STATES"PATENT' OFFICE.

GRANVILLE T. WOODS, OF OINCINNATI, OHIO, ASSIGNOR TO THE VVOQDS ELECTRICCOMPANY.

TEEPHONE SYSTEM AND AP'PARATUS.

SPECIPICATIONforming part of Letters Patent No. 371,241, dated October11, 1887.

Application filed June 1, 1885. Serial No. 167,140. (No model.)

creased force of transmission of the impulses controlling the action ofthe diaphragm at the receiving end 5 also, to obviate the disturbingeffects now attributed to induction from neighboring lines.

The nature of my invention will be more clcarly understood from thesubjoined description, in connection with the accompanying drawings,forming part of this specification, in which the parts referred to areindicated by letters of reference.

In the drawings, Figure 1 is a diagram of the entre system arranged foruse;` Fig. 2, a graphical representation of the electrical current asmodified and utilized in the transmission of speech or sound by myinvention; Fig. 3, an enlarg'ed Vertical cross section of thetransmitting-instrument; Fig. 4, a Vdetached sideelevation of the'Vibratoi'; Fig. 5, a diagram explanatory of the construction of theinduction-coil and connections; Figs. 6 and 7, detail Views of thereceiving instrument.

My invention differs from the ordinary methods of electricaltransmission of speech in two essential particulars: First, I employ inthe primary or local circuit under control of the sending-diaphragm anon-,continuous or intermittent current, which by the action of thesending-diaphragm is alternately shunted by media of varyingconductivity in opposite directions through the primary of aninductioncoil, producing, second, alternating currents of oppositepolarity in the line-circuit.

By the first mentioned feature I obtain a primary of the coil, and bythe latter a reversal of the polarity of the diaphragm in thereceiving-instrument, whereby the diaphragm is both attracted andrepelled, thereby increasing the range and force of its Vibrations andproducing more yigorous air-vibrations and louder sounds. I also obtaina more forcible transmitting-current and the counter action of staticeffects, whereby I am able to transmit through longer distances.

An explanation of 'the principles involved will be given in connectionwith the following description of the form of apparatus illustrated inthe drawings. Adesignates the monthpiece, and A' the ordinary diaphragm,of a transmitting apparatus. In rear of the diaphragm is suspended avibrator or pivoted arm, O, connected below by a light rod, B, centrallywith the diaphragm, so as to vibrate in unison with the diaphragm underthe impulses of sound delivered upon the latter. The bracket D, fromwhich the vibrator O is suspended, is extended laterally, and from itsextended arms are suspended two pendulous bars or conductors, F F', atopposite sides of the vibrator C, and at the lower end of eachof thebars F F' is a carbon electrode, c c', one upon each, held by anadjusting-screw threaded through its bar. The carbon electrodes rest atall times against contact-buttons d d', attached to the vibrator O, oneat each side, and from these contacts depend conducting-wires c e', thetwo connecting with opposite ends of the primary of an induction-coil,G. Midway of the said primary is attached a conducting- Wire, f,extended to a battery, H, thence to an automatic circuit-breaker orrheotome, I, and thence by Wire g to the bracket ID. The Vibrator Obeing insulated, the local circuit thus formed is as follows: Battery Hto rheotome I, thence by wire g to bracket D, thence by a loop,including the duplicate pendulous bars F F', carbons c c', contacts dd', wires e e', and the ends of the primary of inductioncoil G, to thecenter connecting-wire, f, and back to battery. Theline-wire hh',including the secondary of the coil G.isshown extending to a receiver,J, at one end and to ground at the other.

The apparatus is to be carefnlly adj usted,so that when normally at restthe local batterycurrent will divide at the loop and pass equally at thesides of the vibrator and into the induction primary from opposite endsto the center,

IOO

thereby establishing an cquilibrium of inducing effects of oppositepolarities.

The action of the rheotome will be explained later.

If, now, the diaphragm A'be set in vibration by sound-Waves, thevibrator O will at once partake of its movements, and the equilibrium ofresistances between the carbon electrodes c c' being destroyed thedivided current will alternately predoininate at one side or the otherof the vibrator through the pendulous bars F F' and wires e'e', andconsequently alternate in force and direction through the respectiveends of the induction primary G,.with the effect of setting upinducedcurrents of reversed polarity in the induction secondary and linei hJL'. Vln order to trace and analyze this action it should beremembered that sound effects in transmission are wholly converted intoelectrical impulses,and that all overtones and other delicateconstituents of ordinary speech are also converted into and transmittedas L`electrical vibrations or pulsations of an intensity (range ofmovement) and suecessive rapidity corresponding with the sound-Wavesactuating the diaph-ragm. So far as concerns the mere transmission overthe line, it is immaterial what is the polarity of the induced current.The change from a current of one polarity to a current of the other inthis case does not impede or affect the character of the impulses, forthe reason that these are produced by the responsive variations ofresistance in the carbon electrodes, and these Variations are alwaysreferable to a common neutral point of perfect equilibrium, whence thevariations depart and to which they again return. This Vwill be perhapsclearer by taking into consideration the action of thereceiving-instrument, which weV may suppos'e to embody a diaphragmcontrolled by the action of a magnet. Ordinarily, the diaphragm iscontrolled solely by a constant attraction of varying force opposed bythe elasticity of the diaphragm itself; but evenrhere each Suddenimpulse or increase of attraction is followed'by an elastic reaction ofthe diaphragm, whence the necessary range of movement is obtained.Where, however, as in the present case, the impulses due to currents ofone polarity are succeeded by corresponding impulses of the oppositepolarity, the receiVing-diaphragm is controlled, not solely byattraction, but by an alternating repulsion and attraction, by which therange of movement of the receiving diaphragm is increased and loudersound effects produced. Thus the action of my invention, as comparedWith the common method of transmission by a continuous current ofvarying intensity, is analogous to that of a double-acting steam-engineas compared with a singleacting engine. i V

It remains now to consider the function of therheotome in the connectionshown. This will be best understood by considering that induced currentsare produced by alternations of impulse in the primary, and that aninduced current of Stronger electro-motive force is produced by a makeand-break current than by a continuous current of varying impulses. Myobject, therefore, in introducing the rheotonie is to obtain thereby astronger induced current, having a greater carrying-power 1 ntransmission, (so as to be independent of static effects and outsidedisturbing causes and carry longer distances,) and to produce a morevigorous effect at the receiving end.

The action of the rheotome is wholly independent of the transmittingfunctions of the apparatus, excepting as it adds to the effectin degree.Its vibrations being far more rapid than the movenients of thediaphragm, We may represent the current, modified by its action,

graphically, as in Fig. 2 of the drawings, in which the Vertical lines arepresent the electrical impulses, the spaces Z) between being theduration of the breaks, and the relatlve height of the lines a, erectedupon a common base, indicating the relative intenslty of each separateimpulse as a constit'uent of the larger impulse due to the action of thediaphragm.

The action of the rheotome is somewhat modified by that of the apparatusthrough which the local current passes. The slight inertia, which has ofnecessity to be overcome, in thependulous bars F F' and the carbonelectrodes tends to lessen the intervals between successive impulses,and in this respect the action is favorable to the delivery of thetransmitted impulses by approximating a continuous current. It may nowbe explalned, also, that the joint action of the two carbonresistance-contaots and the specified arrangement of the induction-coilprevents any interference by the rheotome action with the induced-linecurrents in the transmission of those impulses corresponding with soundWaves.

For example, if but a single carbon contact and theordinaryinduction-coil were employed the make-and-break of the rheotomewould produce a continuous buzzing noise in the receiving-instrumentwhen the transmittlng-dlaphragm was at rest. In my apparatus, however,whenever the transmitting-diaphragm is at rest a 'neutral condition isestablished in the line by the equilibrium of opposing currents in theprimary. H'e'nce, when the diaphragm is at rest no sound is heard. Whenthe diaphragm is in action, however, the successive impulses due to therheotome are absorbed by the larger impulses due to soundvibrations,into which they enter as constituents, and assist rather than impedethose overtones due to excessive rapidity of vibratory impulses. Thisresult is aided,`also, by the ,partial elimination or shortening of thebreaks produced by inertia, as before explained; and it is also probablethat this inertia being, like -the resistance of the carbons, anunstable element is to some extent controlled by theovertone-vibrations, which approximate those of the rheotome inrapidity, so as to bring about IOO IIO

IIS

a varying sympathetic unison, by which the transmitted' effects aremagnified.

In the production of the induced or carrying currents it will be seenthat there are thns combined two separate conditions or causes, bothtending to produce said current, to wit, the intermittent action of therheotome and the variations of tension produced by the diaphragm.

In the transmission of speech by an unbroken i nndulatory 77current,pwhich is necessarily of low tension, the static conditions,especially on long'lines, operate to impede the transmission, and alsorender theli ne subject to distnrbances by induced currents from otherlines. By the use of my invention, however, involvingalternately-reversed currents, the static effects are practioallyneutralized and the disturban ces referred to are obviated.

I claim as my invention and desire to secure by Letters Patent of theUnited States- 1. In a system of telephonic transmission, thecombination of a local-battery circuit having a loop, a Variableresistance-shunt interposed between the bifurcations of the loop andcontrolled by the receiving-diaphragm, an induction-col having itsprimary interposed betwcen the ends of the loop and centrally connectedback to battery, and a rheotome or automatic circnit-breaker controllingthe local 2. In a system o f telephonic transmission, the local Circuitembodying, in combination, a battery, circuit-breaker or rheotome, abifurcatcd conductor or loop, adj ustable resistancecontacts Controlledby the sound-diaphragm and interposed in the bifurcations of theloopedconductor to shunt the current alternately from one to the other, and aninduction-coil whose primary connects the ends of the looped condnctorand is centrally connected back to battery, substantially as set-forth.

3. In a system of telephonic transmission, the combination of a battery,circuit-breaker, an alternating carbon switch Controlled and operated bythe vocal diaphragm, and branch conductors with a double primaryinductioncoil, said branches uniting at the'center of the coil in asingle return-conductor, snbstantially as set forth.

4:. In combination With the diaphragm A', the connecting-rod B,Vibrating lever O, pendent conductors F F' and carbon contacts d d', therheotome I, and induction-coil G, arranged for operation, as set forth.

In testimony Whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

GRANVILLE T. WOODS.

Vitnesses:

L. M. HosEA, ABRAM MAY.

